Head injury mechanisms in helmet-protected motorcyclists: Prospective multicenter study

Background: In a prospective study, three research groups at Hannover (H) a nd Munich (M) in Germany and Glasgow (G) in the United kingdom collected da ta from motorcycle crashes between July 1996 and July 1998 to investigate h ead injury mechanisms in helmet-protected motorcyclists. Methods: The head lesions of motorcyclists with Abbreviated Injury Score-He ad (AIS(Head)) 2+ injuries and/or helmet impact were classified into direct force effect (DFE) and indirect force effect (IFE) lesions. The effecting forces and the force consequences were analyzed in detail. Results. Two-hundred twenty-six motorcyclists (H, n = 115; M, n = 56; and G , n = 55) were included. Collision opponents were cars (57.8%), trucks (8.0 %), pedestrians (2.3%), bicycles (1.4%), two-wheel motor vehicles (0.8%), a nd others (4.2%). In 25.4% no other moving object was involved. The mean im pact speed was 55 km/h (range, 0-120 km/h) and correlated with AIS(Head). S eventy-six (33%) motorcyclists had no head injury, 21% (n = 48) AIS(Head) 1 , and 46% (n = 103) AIS(Head) 2+. Four hundred nine head lesions were furth er classified: 36.9% DFE and 63.1% IFE. Lesions included 20.5% bone, 51.3% brain, and 28.1% skin. The most frequent brain lesions were subdural hemato mas (22.4%, n = 47) and subarachnoid hematomas (25.2%, n = 53). Lesions of skin or bone were mainly DFE lesions, whereas brain lesions were mostly IFE lesions. Conclusion: A modification of the design of the helmet shell may have a pre ventative effect on DFE lesions, which are caused by a high amount of direc t force transfer. Acceleration or deceleration forces induce IFE lesions, p articularly rotation, which is an important and underestimated factor. The reduction of the effecting forces and the kinetic consequences should be a goal for future motorcycle helmet generations.